1. Technical field of the Invention
The present invention relates to a lens meter to measure optical characteristics of eye glass lenses. More particularly, the invention relates to a lens meter which is applicable to both eye glasses as ordinary products as well as test glasses having trial frames.
2. Related Art Statement
Heretofore, there have known lens meters for measuring the optical characteristics of lenses assembled into eye glass units.
Such a lens meter comprises an eye glass support adapted for supporting the eye glass unit at a given location such that lenses may be substantially horizontal, a light source, such as an LED, adapted for emitting given inspection lights for the measurement of the optical characteristics, light-projecting optical systems adapted for the inspection lights emitted from the light sources to lenses of the eye glass unit supported by the eye glass support almost in optical axis directions of the lenses, respectively, a light detector such as a CCD, and detecting optical systems adapted for leading transmitted lights of the inspection lights through the lenses of the eye glass unit to the light detectors, respectively, wherein the light-projecting optical systems lead the inspection lights emitted from the light sources to the lenses of the eye glass unit supported by the eye glass support almost in the optical axes directions of the lenses, respectively, the detection optical systems lead the transmitted lights through the lenses of three eye glass unit to the light detectors, respectively, and the light detectors detect the light intensity distribution of the transmitted lights to measure the optical characteristics of the eye glass unit, respectively.
Different from a meter device for measuring a single lens, the above lens meter is adapted to measure the optical characteristics of the lenses assembled to an eye glass frame in the form of the eye glass unit. Therefore, as shown in FIG. 21, the eye glass support comprises two sandwiching members 21 and 22, which are displaceable nearer or remoter relative to each other and are adapted to sandwich the outer edge of the eye glass unit in cooperation with each other. The sandwiching members 21 and 22 sandwich the outer edge of the frame in a case of a framed eye glass unit, whereas the sandwiching members 21 and 22 sandwich the outer edges of the lenses in the case of a frame-less eye glass unit. Thereby, the lenses of the eye glass unit are fixed at given locations for measurement.
From the standpoint of the posture stability of the eye glasses when set, the eye glass support including the sandwiching members 21 and 22 generally supports the eye glass unit such that the lenses are substantially horizontal. In the lens meter 100 shown in FIG. 21, supporting pins 23 and 23 erected on an under side of the lenses are adapted to support the under faces of the lenses. See JP-A 2002-202219, JP-A 2002-257680, JP-A 2002-257681, JP-A 2002-296549 and JP-A 2003-194670.
The above-mentioned conventional lens meter is mainly used for measuring the optical characteristics of the eye glass unit as a product. There is also a demand, however, to measure the optical characteristics of detachable lenses 12 (See FIG. 13(b)) fitted to a so-called trial frame 11 (See FIG. 13(a)) which is used for examination of visual acuity, etc. before the product eye glass unit is produced. In this case, the inspection glass unit consisting of the trial frame 11 and the detachable lenses 12 fitted to the trial frame 11 needs to be supported by the glass unit support.
However, if the inspection glass unit 10 is set in the same manner as in the case of the ordinary eye glass unit as a product, as shown in FIG. 22, the sandwiching member 21 (or 22) may touch a tab 12c provided at the detachable lens 12 and turn the detachable lens 12 together with the tab 12c relative to the frame 11.
When the detachable lens 12 is an astigma-correcting lens, the lens 12 is turned to make an angle of a cylindrical axis 12 of the lens different from a set one, so that the target optical characteristics cannot be measured.
Further, the eye glass unit is sandwiched by the sandwiching members 21, 22 such that the lights passing the optical axes of the glasses of the eye glass unit are inputted into almost the centers of the light detectors, respectively. However, even if the detachable lens 12 of the inspection glass unit is not turned, it may be that one of the sandwiching members, 21, holds the frame 11 via the tab 12c between the other, and thus the optical axis 12d of the lens 12 is apart from the supporting pin 23 deposited at a location corresponding to almost the center of the optical detector, by a distance L5 corresponding to a projected amount of the tab 12c from the frame 11. As a result, the light passing the optical axis 12d of the lens 12 is not inputted into almost the center of the optical detector, so that measurement results may be obtained at good precision.